Mineral Analysis

Using Atomic Absorption Spectroscopy (AAS): The ash obtained from the crude ash content analysis was dissolved in 100 ml 6N HCl quantitatively. The solution is appropiately diluted and aspirated in to the nebulizer of flame AAS (Model: GBC 932 B Plus) to determine the dissolved metal content.

Calculation

The concentration of metal is detected in mg/l or ppm
Metal mg/100g = (Concentration of metal in ppm x volume made)/ weight of sample

Using Inductively Coupled Plasma Mass Spectrometry (ICP/MS): Dried fish powders (0.5g) were weighted in glass digestion bombs and 3 ml suprapure HNO3 was added to the samples. The bombs were firmly closed and put in the microwave oven (MDS-Anton Paar, Multiwave 3000) for digestion under controlled pressure. The basic program of the microwave digestion is given in Table 1. After digestion, the glass bombs were cooled and the mineralized samples were diluted to 50 mL with milliQ water. The micro minerals iron, copper, zinc and manganese were directly analyzed in ICP-MS (Thermo, X series 2) whereas the macro minerals were analyzed after appropriately diluting the mineralized samples. A multi element stock standard was used, after appropriate dilution for instrument calibration and sample spiking (1.09494.0100 and 1.09492.0100, E. Merck). The ICP-MS operation and measurement conditions are given in Table 2.

Table 1.Microwave digestion programme

Step	Power (W)	Ramp time (min)	Hold time (min)
1	300	05.00	05.00
2	400	10.00	10.00
3	600	10.00	05.00

Table 2.The ICP- MS operating conditions and measurement conditions

Operating Conditions
Spray chamber	Cyclonic Quartz
RF Power (W)	1398
Plasma Gas Flow (L/min)	13.0
Nebuliser gas flow rate (L/min)	0.98
Auxilary gas flow rate (L/min)	0.5
No. of replicates	3
Isotopes	23Na, 39K, 43Ca, 23Mg,54Fe, 55Mn, 66Zn, 65Cu,
Delay Time (sec)	5
Sample Flush Time (sec)	30
Flush pump rate (rpm)	100
Analysis pump rate (rpm)	40

Reference

• Mohanty BP, Paria P, Das D, Ganguly S, Mitra P, Verma A, et al, (2012) Nutrient profile of giant river-catfish Sperata seenghala (Sykes). National Academy of Science Letter 35:155-161.